When to Plant Onions in Kentucky
The backbone of the kitchen garden. Choose short-day, intermediate, or long-day varieties based on your latitude.
The Short Answer
Kentucky Frost Dates
Your planting dates depend on which part of Kentucky you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Northern Kentucky | 6a, 6b | Apr 15 - May 1 | Oct 5 - Oct 20 |
| Central Kentucky | 6b | Apr 10 - Apr 25 | Oct 10 - Oct 25 |
| Western Kentucky | 6b, 7a | Apr 5 - Apr 20 | Oct 15 - Nov 1 |
Onions Planting Schedule for Kentucky
Northern Kentucky (Zones 6a, 6b)
Average last frost: Apr 15 - May 1 · Average first frost: Oct 5 - Oct 20
Central Kentucky (Zones 6b)
Average last frost: Apr 10 - Apr 25 · Average first frost: Oct 10 - Oct 25
Western Kentucky (Zones 6b, 7a)
Average last frost: Apr 5 - Apr 20 · Average first frost: Oct 15 - Nov 1
Growing Onions in Kentucky
Onions in Kentucky's Climate
Long-day onions are your type. Plant sets or transplants as soon as ground can be worked in spring. For the largest bulbs, start from seed indoors 10-12 weeks before last frost. Your June day length (15+ hours) triggers proper bulbing. Cure in a warm, dry location for 2-3 weeks before storage.
Soil Considerations for Kentucky
Clay soils over limestone bedrock. Naturally alkaline. Good for many vegetables with amendment. Excellent for root crops in some areas. Loose, well-drained soil is especially important for onions since the edible portion grows underground. If your soil is heavy clay, consider raised beds.
Kentucky Climate & Growing Season
Mild, four-season climate. Adequate rainfall. Hot, humid summers. Good growing season. Onions can handle frost well, which is an advantage in Kentucky's climate. You can push planting dates earlier in spring and extend into fall.
Growing season length varies across Kentucky: Northern Kentucky (6a, 6b) has a last frost around Apr 15 - May 1, while Western Kentucky (6b, 7a) sees frost end around Apr 5 - Apr 20. This difference matters for onions — but onions handle frost well, so the timing difference is less critical.
Growing Tips
Day length triggers bulbing. Northern gardeners need long-day varieties. Southern gardeners need short-day varieties.
Companion Planting
Plant onions alongside these companions for better growth:
Keep onions away from:
The Bottom Line
Last reviewed: March 29, 2026